Sub-Sampling
Parallel MRI with Unipolar Matrix Decoding

Doron Kwiat1

1DK Computer College, Tel-Aviv, Israel

A
method is proposed of parallel array scan, where signals from coils are
combined by a summing multiplexer and decoded by unipolar matrix inversion is
suggested, which reduces acquisition channels to a single pre-amp and A/D.
The results would be, an independent individual separated signals as if
acquired through multiple acquisition channels, and yet at a total
acquisition time similar to acquisition time of multiple channels, Background
In a standard parallel array technology, N coils simultaneously cover N FOVs
by reading N k-space lines simultaneously over N independent data sampling
channels. These k-space lines are phase weighted to maximize SNR and then FT
converted to N independent images with an increased SNR[1]. In current
accelerated PI techniques, some of K-space lines are skipped physically, and
are replaced by virtual k-space substitutes using preumed spatial
sensitivities of the coils in the PE direction [2-5].Based on the method described recently
[6,7] a new scanning procedure is described here. The Method 1.Have all coils
be connected through a single summing multiplexer unit (MUX) which allows, at
our discretion, selecting N-1 coils to be actively connected while a single
coil is deactivated electronically, to a single summing common output (SCO).
Let the summed signal from these N-1 coils be sampled by the single
acquisition channel (ACQ) having a single pre-amp and single A/D. 2.Scan
1/Nth of the total k-space lines while having N-1 coils actively connected to
the ACQ by the MUX unit. Repeat the above scan procedure over another 1/Nth
part of k-space, this time with another set of N-1 coils actively connected,
and 1 coil deactivated. Keep these scan procedures N times, until all k-space
lines were acquired over all N possible permutations of selections of N-1 coils
out of N. 3. There are now exactly N summed acquisitions at our hands. Using
an inverse of a unipolar matrix, these can be now decoded back to the
original individual k-space lines